Inert gas lamps, such as the neon lamps used in many small signs, displays and advertisements require a power supply which provides sufficient voltage in a pulsed or switched mode to activate the gas in the lamp.
A typical sign or display has a light skeleton-like, metal frame that holds the inert gas tubing in place. The prior art devices generally use a large, heavy, 60-cycle, high voltage transformer mounted at the bottom of the sign. A typical sign, without the transformer, weighs approximately six pounds while the standard transformer weighs ten pounds or more.
Unfortunately, inert gas signs are generally much too fragile to support the weight of these transformer. As a consequence, a high percentage of signs arrive at their shipping destination with broken lamp tubing. Additional packing material placed around the transformer does not completely alleviate this shipping and handling problem.
The present invention is a power supply for inert gas lamps which is substantially smaller and lighter weight than the prior art power supplies for neon lamps. The new power supply achieves its lower weight by using switching frequencies of at least 25 KHz and a relatively small, loosely coupled output transformer. The power supply's output transformer also has a high Q factor during open circuit conditions, allowing a relatively small transformer to produce the high voltages required for initial ignition of a cold cathode inert gas lamp.
A surprising benefit of the circuit arrangement used in the present invention is that it enables ignition or activation of the inert gas in the lamp with a relatively low input voltage, and complete control over the portion of the lamp or bulb which is activated or lit. By varying the input voltage into the power supply, the portion of the bulb which is lit can be smoothly and controllably varied from zero to 100 percent of the bulb--creating the visual effect that activated gas is flowing through the lamp.
The present invention also includes a control module or visual display function controller which can automatically control and adjust the portion of the bulb which is lit. The portion of the bulb that is lit can therefore be automatically adjusted over time to any point between zero and 100 percent, and this feature can be used with neon bulbs of any length that can be powered by conventional neon bulb power supplies.
It is therefore an object of the present invention to provide a power module for inert gas lamps which is usually small and light weight, and which activates the lamp using high frequency--high voltage electrical power.
Another object of the present invention is to provide a power module for an inert gas lamp, the power module having an output power level which is adjustable so that the portion of the lamp which is lit can be smoothly and controllably varied from zero to 100 percent of the lamp.